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622: Human Imaging I > General Principles and Evaluation of Tissue > Flashcards

General Principles and Evaluation of Tissue Flashcards

1
Q

What is positive predictive value?

A

Given a positive test result, the probability that the individual has the condition

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2
Q

What is negative predictive value?

A

Given a negative test result, the probability that the individual does not have the condition

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3
Q

What is sensitivity?

A

Given that the individual has the condition, the probability that the test will be positive

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4
Q

What is specificity?

A

Given that the individual does not have the condition, the probability that the test will be negative

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5
Q

What is positive likelihood ratio?

A

Given a positive test, the increase in odds favoring the condition

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6
Q

What is negative likelihood ratio?

A

Given a negative test, the decrease in odds favoring the condition

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7
Q

5 Sources of error in imaging studies (same as any other diagnostic tests)

A
  • Images from one patient may be mistaken for those of another patient
  • Wrong extremity imaged
  • Obvious injuries are imaged while other injuries missed
  • Areas of referred pain rather than source of symptoms may be imaged
  • Images may be misinterpreted by radiologist or referring provider
  • Poor quality images
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8
Q

How do DPTs order images?

A

PTs may recommend type of imaging and appropriate sequences or views, but they must first understand the most current diagnostic standards
**US Army DPTs (direct access) hold
privileges for ordering imaging studies

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9
Q

What must the PT give the radiologist when requesting images?

A
  • Description of mechanism of injury (MOI)
  • Location of suspected pathology or areas of symptoms

*They appreciate brief but anatomically correct descriptions

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10
Q

What 2 things must you consider when interpreting images?

A

1) Comprehensive History

2) Physical Examination

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11
Q

What do radiologists often suggest on their official reports?

A

Clinical correlation of imaged pathology

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12
Q

Who’s job is it to interpret diagnostic images?

A

The radiologist

Info from the pt examination combined with this interpretation of images may reveal overlooked pathology on the official reading (PT responsibility)

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13
Q

3 Categories of Imaging

A

1) Reflective Imaging
2) Ionizing Radiation Imaging
3) Emission Imaging

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14
Q

2 Examples of reflective imaging

A

1) Ultrasound

2) Magnetic Resonance Imaging (MRI)

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15
Q

How does reflective imaging work?

A

Energy is inserted into the system, captured, and converted into an image when it is returned

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16
Q

3 Examples of ionizing radiation imaging

A

1) Standard X-Rays
2) Digital X-Rays
3) Computed Tomography (CT)

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17
Q

How does ionizing radiation imaging work?

A

Patient is exposed to ionizing radiation (associated risk) that penetrates matter and creates collectable image through the power of a computer

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18
Q

Ionizing Radiation is capable to produce an image or “slice” as narrow as __ mm thick

A

3

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19
Q

The computer software converts the x-rays that penetrate the body into ____ units.

A

Hounsfield

20
Q

Hounsfield units represent how many levels of specificity between black and white?

A

over 2000 levels

21
Q 
Water = \_\_\_ units
Air  =  \_\_\_ units
Metal = \_\_\_ units
A

0
-1000
1000

22
Q

What is the imaging of choice for evaluating bony pathology?

A

CT

23
Q

What is the imaging of choice for evaluating soft tissue pathology?

A

MRI

24
Q

Example of Emission imaging

A

Bone scan

25
Q

How does emission imaging work?

A

Blood drawn and tagged with radiopharmaceutical agent, reintroduced to body, and allowed to circulate throughout entire body. As the radiopharmaceutical agent decays, it emits γ-rays. After about 2 or 3 hours the body is scanned with a scintillation camera to collect γ emissions which produce an image that demonstrates areas of increased metabolic activity (increased circulation)

26
Q

What does a bone scan tell you?

A

It will tell you if an area demonstrates increased metabolic activity (cancer) but not what is causing increased metabolic activity

27
Q

Bone scans are non-____ and not _____.

A

Specific

Diagnostic

28
Q

When are bone scans used?

A

When trying to identify occult (nonrecognizable) injuries to skeletal system, demonstrating degenerative changes and for documenting extent of certain metastatic lesions

29
Q

What are the most expensive types of imaging?

A

CT and MRI are the most expensive, followed by bone scans, and than standard films

30
Q

What is the most common form of imaging?

A

Standard X-Rays (aka plain or routine film)

31
Q

How do these conventional radiographs work?

A

They use ionizing radiation to produce high-resolution analogue images on specialized film

32
Q

What are the 4 major densities of x-ray production?

from least to most dense

A

1) Air
2) Fat
3) Fluid
4) Bone

33
Q

Air is the most radiolucent, what does that mean?

A

It absorbs the least number of particles from the beam which results in the darkest areas of the negative/film/plate

34
Q

Where is air normally found on the film?

A

within the trachea, lugs, and colon

35
Q

Fat is the also radiolucent, but absorbs ___ of the beam than air

A

MORE

36
Q

Where is fat found on the film?

A

Varies between individuals, but can be found from subcutaneous tissue to pericardium and omentum surrounding the intestines

37
Q

What does fluid represent on a film?

A

varying densities of soft tissue organs and muscle

38
Q

What substance is the most dense?

A

Bone (represents white on the film)

39
Q

Bone itself also varies in density. Cortical (outer) bone is ___ dense than cancellous (inner) bone

A

Much More

40
Q

Bone is not called radiolucent rather it is considered radio-_____.

A

Opaque

41
Q

Metals are completely radio-____.

A

opaque (therefore the least radiolucent) and appear white on a film

42
Q

Typically what are radiographs used for?

A
  • to demonstrate bone origin pathology
  • relationship of bone structures
  • relationship of foreign objects to skeletal structures
43
Q

Are plain film radiographs sensitive to subtle pathology? What does this mean in reference to test results?

A

No, a significant change to the structure of bone must occur before radiographs reveals it.
This means that the chance of a false negative is high for subtle, early-stage pahtologies

44
Q

What percent change in bone density is required in order for an x-ray to detect it?

A

30-40%

45
Q

In order to reduce the radiation exposure and resultant cancer risk to breasts and the thyroid gland what view should be selected?

A

Posterior-to-anterior

46
Q

How many exposures are required?

A

Minimum of two exposures taken at 90° to one another

47
Q

How many exposures are required to cervical and lumbar spine?

A

five exposures each

622: Human Imaging I (7 decks)

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